Liquid crystal display having a modified electrode array

ABSTRACT

A liquid crystal display having electrodes on a single substrate. A transparent planar electrode elongated in the transverse direction is formed on the inner surface of a substrate, and an insulating film is deposited thereon. A plurality of linear electrodes, which are elongated in the longitudinal direction and either transparent or opaque, are formed on the insulating film. Potential difference between the planar and the linear electrodes generated by applying voltages to the electrodes yields an electric field. The electric field is symmetrical with respect to the longitudinal central line of the linear electrodes and the longitudinal central line of a region between the linear electrodes, and has parabolic or semi-elliptical lines of force having a center on a boundary line between the planar and the linear electrodes. The line of force on the planar and the linear electrodes and on the boundary line between the planar and the linear electrodes has the vertical and the horizontal components, and the liquid crystal molecules are re-arranged to have a twist angle and an tilt angle. The polarization of the incident light varies due to the rearrangement of the liquid crystal molecules.

BACKGROUND OF THE INVENTION

[0001] (a) Field of the Invention

[0002] The present invention relates to a liquid crystal display (LCD).More particularly, the present invention relates to an LCD having amodified electrode array.

[0003] (b) Description of the Related Art

[0004] Generally, an LCD is a display having two substrates and a liquidcrystal layer therebetween. A plurality of electrodes are formed on theinner surfaces of either or both the substrates, a pair of polarizersare attached to the outer surfaces of the substrates, and the liquidcrystal layer serves as an optical switching medium. When a potentialdifference is applied to the electrodes, liquid crystal molecules arere-arranged due to the potential difference, and the re-arranged liquidcrystal molecules scatter the incident light, which have passed throughone of the polarizers, or change the transmission characteristics of thelight, thereby controlling the transmittance of the light out of theother polarizer (which is usually called an analyzer) and displayingimages.

[0005] As an example of a conventional LCD, U.S. Pat. No. 5,576,861discloses a twisted nematic LCD (TN-LCD) where an upper electrode and alower electrode formed respectively on the inner surfaces of upper andlower substrates and a nematic liquid crystal material is injectedtherebetween, and where the liquid crystal molecules are twisted withbeing parallel to the substrates. In the above LCD, the potentialdifference between the two electrodes generated by applying voltages tothe upper and the lower electrodes yields an electric fieldperpendicular to the substrates. The liquid crystal molecules arere-arranged such that the torque due to the dielectric anisotropy andthe torque due to the aligning treatment is balanced with each other.The torque due to the dielectric anisotropy forces the long axes of theliquid crystal molecules to be parallel to the field direction, and themagnitude of this torque depends on the intensity of the electric field.The elastic torque generated by the aligning treatment such as rubbingforces the long axes of the liquid crystal molecules to be parallel to apredetermined direction. When the director of the liquid crystal twistsby 90 degrees on going from the lower electrode to the upper electrode,and the polarization directions of the polarizers are perpendicular toeach other, the polarization of the incident light, in absence of theelectric field, rotates by 90 degrees and thus the light passes throughthe analyzer, thereby causing white state. However, when sufficientelectric field is applied to the liquid crystal layer, since theincident light passes through the liquid crystal layer without changingits polarization, the light cannot pass through the analyzer, therebycausing black state.

[0006] As another example of a conventional LCD, U.S. Pat. No. 5,598,285discloses an LCD, where two linear electrodes parallel to each other areformed on either of the two substrates, and a liquid crystal layer liesover the region between the two electrodes, and where the liquid crystalmolecules are aligned parallel to the substrates. In this LCD, thepotential difference between the two electrodes yields an electric fieldsubstantially parallel to the substrates and perpendicular to the twoelectrodes. The liquid crystal molecules are re-arranged such that thetorque due to the dielectric anisotropy and the elastical torque due torubbing are balanced with each other. When the polarization directionsof the polarizers are perpendicular to each other, in absence ofelectric field, the crossed polarizer blocks the incident light andmakes the liquid crystal display to be in black state. However, whensufficient electric field is applied to the liquid crystal layer, thepolarization of the incident light varies and the light passes throughthe analyzer, thereby causing white state.

[0007] The above-mentioned LCDs have disadvantages described hereinafterrespectively.

[0008] The principal disadvantage of the TN-LCD is its narrow viewingangle. In the TN-LCD, the larger an angle made by the direction of theuser's eye and the direction normal to a surface of a display, thelarger the value Δn d where birefringence Δn is the difference of therefractive indices between in the directions of the long axes and theshort axes of the liquid crystal molecules and d is the thickness of theliquid crystal layer. Accordingly, the contrast, which is defined as theluminance of the brightest state divided by that of the darkest state,abruptly decreases. In addition, gray inversion phenomenon also occurs.Accordingly, the viewing angle at which the contrast is equal to 10 isvery narrow, and thus image quality is abruptly deteriorated when viewedat an angle larger than the viewing angle.

[0009] To compensate the viewing angle, methods using phase differencecompensating films are suggested in U.S. Pat. No. 5,576,861, but theyhave disadvantages in manufacturing cost and the number of the processsteps since the phase difference compensating films are additionallyattached. Furthermore, the satisfactory viewing angle may not be stillobtained even though the phase retardation compensation films are used.

[0010] The U.S. Pat. No. 5,598,285 has disadvantages in powerconsumption and aperture ratio. The LCD disclosed in the above U.S. Pat.No. 5,598,285 has an electric field of which strength is dependent onthe positions, that is, the field strength is weaker as far from theelectrodes. Therefore, in order to obtain sufficient field strength atthe far point from the electrodes, high driving voltage is required. Inaddition, since all the electrodes are formed on one substrate andstorage capacitors are formed to obtain sufficient capacitance, theaperture ratio is small.

[0011] In the meantime, since the liquid crystal display is a passivedisplay, it requires an external light source. A white light is usuallyused for the light source of the liquid crystal display, and red, greenand blue color filters are used for color display. The color filters areformed on one of the substrates, and a black matrix for preventing lightleakage at the boundaries of the color filters is formed therebetween.

[0012] The light from the tight source changes its properties, such aspolarization, in the liquid crystal layer, and the transmittance of thelight depends on the wavelength of the light. The transmittance alsodepends on the driving mode of the liquid crystal display.

[0013] In the case of TN LCDs, the transmittance of the blue lightdiffers from those of the red and green lights by 10%. Moreover, the IPSLCD has the difference of the transmittances of the blue, red and greenlights more than 40%.

[0014] In order to reduce the difference of the transmittance, twomethods are conventionally used, one using a backlight unit and adriving circuit having additional characteristics and the other making acell gap to be different for the pixels of different colors by adjustingthe height of the color filters. However, the former method may increasethe yield cost and the number of process steps, and the latter may causeuneven rubbing.

SUMMARY OF THE INVENTION

[0015] An object of the present invention is to obtain a wide viewingangle.

[0016] Another object of the present invention is to reduce powerconsumption of the liquid crystal display.

[0017] Still another object of the present invention is to enlarge theaperture ratio.

[0018] In order to accomplish the above-mentioned objects, the array ofthe electrodes of the LCD is modified.

[0019] First electrodes and second electrode insulated from each otherare overlapped with each other at least in part. The second electrodeforms a continuous plane between the first electrodes, and one pixelincludes at least one first electrode and one second electrode.

[0020] The potential difference between the two electrodes generated byapplying voltages to the electrodes yields an electric field. The shapeof an electric line of force is semi-ellipse or parabola having a centeron a boundary line or a boundary region between the first electrode andthe second electrode, whereby the electric field on the electrodes hasthe vertical and the horizontal components.

[0021] The liquid crystal molecules on the first or the second electrodeand on the boundary region between the two electrodes are re-arranged tohave a twist angle and a tilt angle due to the vertical and thehorizontal components of the electric field. Therefore, the polarizationof the incident light varies by the rearrangement of liquid crystalmolecules.

[0022] As described above, a wide viewing angle may be obtained sincethe liquid crystal molecules are re-arranged to have both the twistangle and the tilt angle.

[0023] In addition, the liquid crystal molecules on the first electrodeand the second electrode contribute to displaying images since theelectric field has the vertical and the horizontal components on thefirst electrode and the second electrode as well as on the boundaryregion between the two electrodes.

[0024] In addition, power consumption is low since the strength of theelectric field is large on the boundary region between the firstelectrode and the second electrode.

[0025] In addition, aperture ratio may be enlarged since a storagecapacitor for obtaining sufficient storage capacitance is notadditionally required since the two electrodes are overlapped via aninsulating film when using a thin film transistor (TFT) as a switchingelement.

[0026] Additional objects and advantages of the present invention areset forth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice of theinvention. The objects and advantages of the invention will be realizedand attained by means of the elements and combinations particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, illustrate embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention.

[0028]FIG. 1 is a layout view of electrodes of a liquid crystal display(LCD) according to a first embodiment of the present invention;

[0029]FIG. 2 is a cross-sectional view taken along line II-II′ in FIG.1, which shows both upper and lower substrates as well as equipotentiallines and lines of electrical force between the two substrates;

[0030]FIG. 3 illustrates the twist angle of liquid crystal molecules inthe first embodiment of the present invention;

[0031]FIG. 4 is a graph illustrating the variation of the twist angle ofthe liquid crystal molecules as a function of the horizontal positionaccording to the first embodiment of the present invention;

[0032]FIG. 5 is a graph illustrating the variation of the twist angle ofthe liquid crystal molecules as a function of height according to thefirst embodiment of the present invention;

[0033]FIG. 6 shows the tilt angle of the liquid crystal moleculesaccording to the first embodiment of the present invention;

[0034]FIG. 7 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of height according to thefirst embodiment of the present invention;

[0035]FIG. 8 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of horizontal positionaccording to the first embodiment of the present invention;

[0036]FIG. 9 is a graph illustrating the transmittance as a function ofhorizontal position in the LCD according to the first embodiment of thepresent invention;

[0037]FIG. 10 is a graph illustrating the transmittance as a function ofapplied voltage in the LCD according to the first embodiment of thepresent invention;

[0038]FIG. 11 is a graph illustrating a viewing angle in the LCDaccording to the first embodiment of the present invention;

[0039]FIG. 12 illustrates the twist angle of liquid crystal molecules inthe second embodiment of the present invention,

[0040]FIG. 13 is a graph illustrating the variation of the twist angleof the liquid crystal molecules as a function of the horizontal positionaccording to the second embodiment of the present invention;

[0041]FIG. 14 is a graph illustrating the variation of the twist angleof the liquid crystal molecules as a function of height according to thesecond embodiment of the present invention;

[0042]FIG. 15 shows the tilt angle of the liquid crystal moleculesaccording to the second embodiment of the present invention;

[0043]FIG. 16 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of height according to thesecond embodiment of the present invention;

[0044]FIG. 17 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of horizontal positionaccording to the second embodiment of the present invention;

[0045]FIG. 18 illustrates the twist angle of liquid crystal molecules inthe third embodiment of the present invention;

[0046]FIG. 19 is a graph illustrating the variation of the twist angleof the liquid crystal molecules as a function of the horizontal positionaccording to the third embodiment of the present invention;

[0047]FIG. 20 is a graph illustrating the variation of the twist angleof the liquid crystal molecules as a function of height according to thethird embodiment of the present invention;

[0048]FIG. 21 shows the tilt angle of the liquid crystal moleculesaccording to the third embodiment of the present invention;

[0049]FIG. 22 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of height according to thethird embodiment of the present invention;

[0050]FIG. 23 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of horizontal positionaccording to the third embodiment of the present invention;

[0051]FIG. 24 illustrates the twist angle of liquid crystal molecules inthe fourth embodiment of the present invention;

[0052]FIG. 25 is a graph illustrating the variation of the twist angleof the liquid crystal molecules as a function of the horizontal positionaccording to the fourth embodiment of the present invention;

[0053]FIG. 26 is a graph illustrating the variation of the twist angleof the liquid crystal molecules as a function of height according to thefourth embodiment of the present invention;

[0054]FIG. 27 shows the tilt angle of the liquid crystal moleculesaccording to the fourth embodiment of the present invention;

[0055]FIG. 28 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of height according to thefourth embodiment of the present invention;

[0056]FIG. 29 is a graph illustrating the variation of the tilt angle ofthe liquid crystal molecules as a function of horizontal positionaccording to the fourth embodiment of the present invention;

[0057]FIG. 30 is a layout view of an LCD according to a fifth embodimentof the present invention;

[0058]FIG. 31 is a cross-sectional view taken along the line V-V′ inFIG. 30;

[0059]FIG. 32 is a layout view of the LCD according to a sixthembodiment of the present invention;

[0060]FIG. 33 is a cross-sectional view taken along line VIA-VIA′ inFIG. 32;

[0061]FIG. 34 is a cross-sectional view taken along line VIB-VIB′ inFIG. 32;

[0062]FIG. 35A is a layout view of the LCD according to a seventhembodiment of the present invention;

[0063]FIGS. 35B and 35C are cross-sectional views taken along linesVII1B-VIIB′ and VII1C-VIIC′ in FIG. 35A;

[0064]FIGS. 36A to 39C shows intermediate structures of the LCD shown inFIGS. 35A to 35C;

[0065]FIG. 40 is a layout vies of the LCD according to an eighthembodiment of the present invention;

[0066]FIGS. 41 and 42 are two different cross-sectional views takenalong line VIIIA-VIIIA′ in FIG. 40;

[0067]FIG. 43 is a cross-sectional view taken along line VIIIB-VIIIB′ inFIG. 40;

[0068] FIGS. 44 to 46 are cross-sectional views of LCDs according to theninth embodiment of the present invention;

[0069]FIG. 47 is a cross-sectional view of an LCD according to the tenthembodiment of the present invention;

[0070]FIG. 48 is a schematic diagram of the electric field andequipotential lines in the LCD according to the tenth embodiment of thepresent invention;

[0071]FIG. 49 is a graph illustrating the transmittance as a function ofapplied voltage in the LCD according to the tenth embodiment of thepresent invention;

[0072]FIG. 50 is a graph illustrating a viewing angle in the LCDaccording to the tenth embodiment of the present invention;

[0073]FIG. 51 is a layout view of an LCD according to an eleventhembodiment of the present invention;

[0074]FIGS. 52 and 53 are cross-sectional views taken along linesXIA-XIA′ and XIB-XIB′ in FIG. 51;

[0075]FIGS. 54A to 57B shows intermediate structures of the LCD shown inFIGS. 51 to 53;

[0076]FIG. 58 is a layout view of an LCD according to an twelfthembodiment of the present invention;

[0077]FIGS. 59 and 60 are cross-sectional views taken along linesXIIA-XIIA′ and XIIB-XIIB′ in FIG. 58;

[0078]FIGS. 61A to 63B show intermediate structures of the LCD shown inFIGS. 58 to 60;

[0079]FIG. 64 is a layout view of an LCD according to an thirteenthembodiment of the present invention;

[0080]FIGS. 65 and 66 are cross-sectional views taken along linesXIIA-XIIA′ and XIIB-XIIB′ in FIG. 64;

[0081]FIGS. 67A to 68B show intermediate structures of the LCD shown inFIGS. 64 to 66;

[0082]FIG. 69 is a layout view of an LCD according to an fourteenthembodiment of the present invention;

[0083]FIG. 70 is a layout view of an LCD according to an fifteenthembodiment of the present invention;

[0084]FIGS. 71 and 72 are cross-sectional views taken along linesXVA-XVA′ and XVB-XVB′ in FIG. 70;

[0085]FIG. 73 is a layout view of an LCD according to an sixteenthembodiment of the present invention;

[0086]FIG. 74 is a layout view of an LCD according to an seventeenthembodiment of the present invention;

[0087]FIGS. 75 and 76 are cross-sectional views taken along linesXVIIA-XVIIA′ and XVIIB-XVIIB′ in FIG. 74;

[0088] FIGS. 77 to 79 are cross-sectional views of LCDs according to theeighteenth to the twentieth embodiments of the present invention; and

[0089]FIG. 80 shows an LCD according to the twenty first embodiments ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0090] A liquid crystal display (LCD) according to the embodiments ofthe present invention will become apparent from a study of the followingdetailed description when viewed in light of the drawings.

[0091] First, the LCD according to the first embodiment of the presentinvention is described in detail with reference to FIGS. 1 to 11.

[0092]FIG. 1 is a layout view of electrodes of an LCD according to thefirst embodiment of the present invention, and FIG. 2 is across-sectional view taken along the line II-II′ in FIG. 1, whichillustrates both upper and lower substrates as well as equipotentiallines and lines of electrical force between the substrates.

[0093] First, the structures of a lower substrate on which electrodesare formed and an upper substrate of the LCD are described in detail.

[0094] A planar electrode 2 made of transparent conductive material suchas indium tin oxide (ITO) is formed on the inner surface of a lowersubstrate 100 made of a transparent insulating material such as, glassor quartz. The planar electrode 2 has a predetermined longitudinal widthand is elongated in the transverse direction. The planar electrode 2 iscovered with an insulating film 3, and a plurality of narrow linearelectrodes 1 which are parallel to each other and elongated in thelongitudinal direction are formed on the insulating film 3. The linearelectrodes 1 may be transparent or opaque. The width of the linearelectrode 1 is equal to or smaller than the distance between the linearelectrodes 1, exactly to say, the distance between adjacent boundarylines of the two adjacent linear electrodes 1. An aligning film 4 madeof polyimide is coated all over the surface, and may be rubbed or not. Apolarizing plate or a polarizer 5 is attached on the outer surface ofthe lower substrate 100.

[0095] On the other hand, an aligning film 6 made of polyimide is coatedon the inner surface of an upper substrate 200, which is opposite thelower substrate 100 and also made of a transparent insulating material.A polarizing plate or an analyzer 7 is attached on the outer surface ofthe upper substrate 200.

[0096] Finally, a liquid crystal layer 500 having optical anisotropy isinterposed between the aligning films 4 and 6 on the substrates 100 and200.

[0097] The light source for the liquid crystal display may be either abacklight unit (not shown) located under the lower substrate 100 or anexternal, natural light which may enter into the LCD through the uppersubstrate 200. In case of reflective type LCD using the natural light,the polarizing plate 5 attached on the lower substrate 100 may not berequired, and it is preferable that the linear electrodes 1 and theplanar electrode 2 are made of opaque material having high reflectancesuch as Aluminum Al. In addition, the lower substrate 100 may be opaque.

[0098] A schematic shape of the electric fields of the above-describedLCD is described with reference to FIG. 2.

[0099] When voltages are applied to the electrodes 1 and 2, the electricfield shown in FIG. 2 due to the potential difference between theelectrodes 1 and 2 is generated. In FIG. 2, solid lines indicateequipotential lines, and dotted lines indicate the lines of electricalforce.

[0100] As shown in FIG. 2, the shape of the electrical field issymmetrical with respect to a longitudinal central line C (actually theline C corresponds to a plane) of a narrow region NR on the linearelectrodes 1 and a longitudinal central line B (actually the line B alsocorresponds to a plane) of a wide region WR between the linearelectrodes 1. The line of force has a semi-elliptical or parabolic shape(hereinafter, the shape of the line of force is referred as asemi-elliptical shape for simplicity) and is generated in a regionbetween the central line C of the narrow region NR and the central lineB of the wide region WR. The vertices of the line of force are in aboundary line A (actually the line A corresponds to a surface) betweenthe narrow region NR and the wide region WR.

[0101] A tangent of the line of force on the boundary line A between thenarrow region NR and the wide region WR is substantially parallel to thesubstrate 100, and that at central points of the narrow region NR and awide region WR is substantially perpendicular to the substrates 100 and200. In addition, the center and the vertical vertex of the ellipse arepositioned on the boundary line A between the narrow NR and the wideregion WR, and two horizontal vertices are positioned in the wide regionWR and the narrow region NR respectively. The ellipse is asymmetricalwith respect to the boundary line A since the horizontal vertexpositioned in the narrow region NR is closer to the center of theellipse than the horizontal vertex positioned in the wide region WR. Inaddition, the density of the lines of force varies dependent on theposition, and thus the field strength also varies in proportion to thedensity of the lines of force. Accordingly, the field strength is thelargest on the boundary line A-A between the narrow region NR and thewide region WR, and it becomes small as goes to the central lines C-Cand B-B of the broad and the narrow regions BR and NR and to the uppersubstrate 200.

[0102] The behaviors of the liquid crystal molecules due to the electricfield are described hereinafter.

[0103] First, the initial states of the liquid crystal molecules aredescribed.

[0104] The two aligning films 4 and 6 are rubbed or exposed toultraviolet light, and the liquid crystal molecules are aligned in onehorizontal direction. The liquid crystal molecules may have somepre-tilt angle with respect to the substrates 100 and 200 but they arealigned substantially parallel to the substrates 100 and 200. Whenviewed on a plane parallel to the substrates 100 and 200, the liquidcrystal molecules are arranged to have a predetermined angle withrespect to the directions parallel and perpendicular to the linearelectrodes 1. The polarizing directions of the polarizing plates 20 and21 are perpendicular to each other, and the polarizing direction of thepolarizer 5 almost coincides with the rubbing direction. The liquidcrystal material inserted between the two aligning films 4 and 6 is anematic liquid crystal having positive dielectric anisotropy.

[0105] It is assumed that the voltages are applied to the linearelectrodes 1 and the planar electrode 2 and the voltage applied to thelinear electrodes 1 is higher than that to the planar electrode 2. Then,the liquid crystal molecules are re-arranged such that the force due tothe electric field, which depends on the direction and the strength ofthe electric field, and an elastical restoring force due to the aligningtreatment are balanced with each other.

[0106] The rearrangement of the liquid crystal molecules due to theelectric field is described in detail.

[0107] For simplicity, it is assumed that a direction perpendicular tothe substrates is z direction, a direction perpendicular to thesubstrates and to the direction of the linear electrodes 1 is xdirection, and a direction parallel to the direction of the linearelectrodes 1 is y direction. That is to say, it is assumed that thedirection from left to right in FIG. 1 is the positive x direction, thedirection upward along the linear electrodes 1 in FIG. 1 is the positivey direction, and the direction from the lower substrate 200 to the uppersubstrate 100 in FIG. 2 is the positive z direction.

[0108] First, the variation of a twist angle, which is defined by theangle made by the projection of the long axis of the liquid crystalmolecule with the x axis or the initially aligned direction onto xyplane parallel to the substrate 100 and 11, is described with referenceto FIGS. 3, 4 and 5.

[0109] As shown in FIG. 3, the rubbing direction is indicated by {rightarrow over (R)}, an x-y plane component of the electric field isindicated by {right arrow over (E)}_(xy), and the polarizing directionor the optical axis of the polarizer 5 is indicated by {right arrow over(P)}, while the angle made by the rubbing direction {right arrow over (R)} with the x axis is represented by ψ_(R), and the angle made by thelong axis of the liquid crystal molecule with the x axis is representedby ψ_(LC). The angle ψ_(P) made by the optical axis of the polarizer 5with the x-axis is equal to ψ_(R) since the optical axis of thepolarizer 5 is parallel to the rubbing direction {right arrow over (R)}.

[0110] The x-y plane component {right arrow over (E)}_(xy) of theelectric field is in the positive x direction from the boundary line Ato the central line B of the wide region WR, and in the negative xdirection from the central line B of the wide region WR to the nextboundary line D.

[0111] The strength of the electric field component {right arrow over(E)}_(xy) is the largest on the boundary lines A and D, and it becomessmaller as goes to the central line B-B, where the strength of theelectric field component {right arrow over (E)}_(xy) is zero.

[0112] The magnitude of the elastical restoring force generated by therubbing process is substantially constant on the xy plane regardless ofposition.

[0113] As illustrated in FIG. 4, the long axis of the liquid crystalmolecule or the molecular axis on the boundary lines A and D issubstantially parallel to the electric field component {right arrow over(E)}_(xy), and makes a large angle with respect to the rubbing direction{right arrow over (R)} since the liquid crystal molecules may bearranged to balance the two forces. However, the closer to the centrallines C and B of the regions NR and WR, the smaller the angle|ψ_(R)−ψ_(LC)| which the molecular axis makes with the rubbing direction{right arrow over (R)}, and the molecular axis on the central lines Band C is in the rubbing direction {right arrow over (R)}. The angle madeby the optical axis of the polarizer 5 with the molecular axis has thesame distribution as the above since the optical axis of the polarizer 5is parallel to the rubbing direction {right arrow over (R)}, and thisangle is closely related to the transmittance of the incident light.

[0114] Various shapes of electric fields may be generated by varying theratio of the widths of the narrow region NR and the wide region WR.Although the narrow region NR on the linear electrodes 1 cannot be usedas the display region when the linear electrodes 1 are opaque, it may bealso used as the display region when the linear electrodes 1 aretransparent.

[0115] On the other hand, the xy plane component of the electric field{right arrow over (E)}_(xy) becomes smaller along the z-axis as goesfrom the lower aligning film 4 to the upper aligning film 6. The elasticrestoring force generated by the aligning treatment is the greatest onthe surfaces of the aligning films 4 and 6, and it is reduced as goes tothe center of the liquid crystal layer between the aligning films 4 and6.

[0116]FIG. 5 illustrates the twist angle made by the molecular axis withthe x-axis from the lower aligning film 4 to the upper aligning film 6along the z-axis. In FIG. 5, the horizontal axis indicates the heightfrom the lower aligning film 4, and the vertical axis represents thetwist angle, where d is the cell gap between the two aligning films 4and 6.

[0117] As illustrated in FIG. 5, the twist angle on the surfaces of thealigning films 4 and 6 is large since the aligning force of the aligningfilms 4 and 6 is great. The twist angle becomes small as goes to thecenter of the liquid crystal layer, and the molecular axis at the centerof the liquid crystal layer is substantially in the direction of theelectric field component {right arrow over (E)}_(xy). The molecular axisjust on the aligning films 4 and 6 is arranged in the rubbing direction{right arrow over (R)}.

[0118] Supposing that the difference of the twist angle between theadjacent liquid crystal molecules is called twist, the twist correspondsto the slope of the curve in FIG. 5. The twist is large near thesurfaces of the aligning films 4 and 6, and it decreases as goes to thecenter of the liquid crystal layer.

[0119]FIGS. 6, 7 and 8 illustrate the variation of the tilt angle whichthe molecular axis makes with x-axis or the initially aligned directionon a plane perpendicular to the substrate, for example, zx plane. FIG. 6illustrates only the substrates 100 and 200 for the purpose ofsimplifying explanation. In FIG. 6, the zx plane component of the {rightarrow over (R)} indicating the rubbing direction in FIG. 3 isrepresented by {right arrow over (R)}_(zx), and the zx plane componentof the electric field is represented by {right arrow over (E)}_(zx),while the angle made by the field component {right arrow over (E)}_(zx)with the x axis is indicated by θ_(E), and the tilt angle made by themolecular axis with the x axis is indicated by θ_(LC). Here, {rightarrow over (R)}_(zx) is in the x direction since the vector {right arrowover (R)} exists on the xy plane assuming a pretilt angle is ignored.

[0120] The magnitude of thy field component {right arrow over (E)}_(zx)and the angle θ_(E) becomes small as goes to the upper substrate 200from the lower substrate 100.

[0121] As described above, the elastic restoring force by the aligningtreatment is the largest on the surfaces of the two substrates 100 and200, and it becomes small as goes to the center of the liquid crystallayer.

[0122] The liquid crystal molecules may be arranged to balance the twoforces. As illustrated in FIG. 7, the molecular axis on the surfaces ofthe substrates 100 and 200 is arranged substantially parallel to thex-axis since the aligning force is the strongest there. Since the forcedue to the electric field becomes relatively stronger compared with thealigning force from the substrates 100 and 200 to a certain point, themagnitude of the tilt angle θ_(LC) increases continuously. Here, thevertex of the curve is formed at a point near the lower substrate 100.

[0123] On the other hand, the angle θ_(E) which the field component{right arrow over (E)}_(zx) makes with the x axis is almost zero on theboundary lines A and D, and it becomes large as goes to the central lineB-B. The magnitude of the field component {right arrow over (E)}_(zx) isthe greatest on the boundary lines A and D, and it is reduced as goes tothe central line B-B.

[0124] The magnitude of the elastic restoring force by the aligningtreatment is constant on the x axis regardless of the position.

[0125] Accordingly, as illustrated in FIG. 8, the tilt angle of theliquid crystal molecule is almost zero on the boundary lines A and D,and it decreases as goes to the central lines C and B. Therefore, thetilt angle of the liquid crystal molecules has the similar distributionsto the angle θ_(E) made by the field component {right arrow over(E)}_(zx) with the x axis, although the tilt angle varies more smoothlythan the angle θ_(E).

[0126] As described above, when the voltages are applied to the twoelectrodes 1 and 2, the liquid crystal molecules are re-arranged to havethe twist angle and the tilt angle. The transmittance of the incidentlight vary due to the variation of the twist angle and the tilt angle.On the boundary lines A and D, there is little variation in the tiltangle along the z axis, but the twist angle varies very much. On thecentral lines B and C, on the other hand, there is little variation inthe twist angle along the z axis but there is a little variation in thetilt angle. Accordingly, both the twist angle and the tilt angle variesin the region between the boundary lines A and D and the central lines Band C. As a result, a transmittance curve as a function of position hasa similar shape to the lines of force.

[0127] The transmittance and the viewing angle characteristics of theLCD according to the first embodiment of the present invention aredescribed with reference to experimental results illustrated in FIGS. 9,10 and 11.

[0128] In the experiment, the linear electrodes 1 was made of the opaquematerial, the widths of the narrow and the wide regions NR was 5 μm and17 μm respectively, the voltage applied to the planar and the linearelectrodes 2 and 1 was 0 V and 5 V respectively, ψ_(R) was 80°, thepre-tilt angle was about 1.5°, and the cell gap was 4.5 μm.

[0129]FIG. 9 is a graphical illustration of the transmittance as afunction of position along the x-axis according to the experiment, wherethe origin is located at the left boundary line of the leftest linearelectrode 1 in FIG. 3.

[0130] As illustrated in FIG. 9, the transmittance is zero in the opaquenarrow region NR, has minima near the central lines B of the wide regionWR, and has maxima in the central region between the boundary lines Aand D and the central lines B.

[0131]FIG. 10 illustrates the tranmittance as a function of the appliedvoltage according the experiment, where the horizontal axis indicatesthe applied voltage, and the vertical axis indicates the transmittance.As shown in FIG. 10, the threshold voltage is about 1.5 V, and thesaturation voltage is about 3 V. Accordingly, it is possible to drivethe LCD of the present invention with the low voltage less than 3V.

[0132]FIG. 11 is a graphical illustration showing the viewing anglecharacteristics according to the experiment. As shown in FIG. 11, theboundary of the region where the contrast is equal to or more than 10 issubstantially over 60 degrees.

[0133] When using optical phase compensating films between thepolarizing plates and the substrates, the viewing angle may becomewider.

[0134] In the above-mentioned embodiment and experiments, it is possibleto modify the kind of the liquid crystal material, the kind of thealigning films, aligning methods, the pre-tilt angle, the polarizingdirections of the polarizing plates, the cell gaps, the kind of thephase difference compensating plates, the material forming theelectrodes, the widths of the electrodes and the distances between theelectrodes. For example, when the linear electrodes 1 are made of thetransparent material, the higher transmittance can be obtained since theliquid crystal molecules on the linear electrodes 1 are used forcontrolling the light

[0135] The modifications of the kind of the liquid crystal and/or ofinitial state are described through second to fourth embodiments.

[0136] The second embodiment uses a liquid crystal having negativedielectric anisotropy.

[0137] The structure of an LCD according to the second embodiment issimilar to the first embodiment, and thus the shape of the electricfield is similar However, the rearrangement of the liquid crystalmolecules due to the electric field is different from the firstembodiment.

[0138] In the initial state, the two aligning films 4 and 6 are rubbedor exposed to ultraviolet flight, and the liquid crystal molecules arealigned in one horizontal direction. The liquid crystal molecules mayhave some pretilt angle of less than 7 degrees with respect to thesubstrates 100 and 200 but they are aligned substantially parallel tothe substrates 100 and 200. When viewed on a plane parallel to thesubstrates 100 and 200, the liquid crystal molecules are arranged tohave a predetermined angle of equal to or less than 45 degrees withrespect to the directions parallel and perpendicular to the linearelectrodes 1. The polarizing directions of the polarizing plates 20 and21 are perpendicular to each other, and the polarizing direction of thepolarizer 5 almost coincides with the rubbing direction. Then theinitial state is black state.

[0139] For simplicity, it is assumed that a direction perpendicular tothe substrates is z direction, a direction perpendicular to thesubstrates and to the direction of the linear electrodes 1 is xdirection, and a direction parallel to the direction of the linearelectrodes 1 is y direction. That is to say, it is assumed that thedirection from left to right in FIG. 1 is the positive x direction, thedirection upward along the linear electrodes 1 in FIG. 1 is the positivey direction, and the direction from the lower substrate 200 to the uppersubstrate 100 in FIG. 2 is the positive z direction.

[0140] First, the variation of a twist angle, which is defined by theangle made by the projection of the long axis of the liquid crystalmolecule with the x axis or the initially aligned direction ontoxy-plane parallel to the substrate 100 and 11, is described withreference to FIGS. 12, 13 and 14.

[0141] As shown in FIG. 12, the rubbing direction is indicated by {rightarrow over (R)}, an x-y plane component of the electric field isindicated by {right arrow over (E)}_(xy), and the polarizing directionor the optical axis of the polarizer 5 is indicated by {right arrow over(P)}, while the angle made by the rubbing direction {right arrow over(R)} with the x axis is represented by 104 _(R), and the angle made bythe long axis of the liquid crystal molecule with the x axis isrepresented by ψ_(LC). The angle ψ_(P) made by the optical axis of thepolarizer 5 with the x-axis is equal to _(ψR) since the optical axis ofthe polarizer 5 is parallel to the rubbing direction {right arrow over(R)}.

[0142] The x-y plane component {right arrow over (E)}_(xy) of theelectric field is in the positive x direction from the boundary line Ato the central line B of the wide region WR, and in the negative xdirection from the central line B of the wide region WR to the nextboundary line D.

[0143] The strength of the electric field component {right arrow over(E)}_(xy) is the largest on the boundary lines A and D, and it becomessmaller as goes to the central line B-B, where the strength of theelectric field component {right arrow over (E)}_(xy) is zero.

[0144] The magnitude of the elastically restoring force generated by therubbing process is substantially constant on the xy plane regardless ofposition.

[0145] As illustrated in FIG. 13, the long axis of the liquid crystalmolecule or the molecular axis on the boundary lines A and D issubstantially perpendicular to the electric field component {right arrowover (E)}_(xy), and to the rubbing direction {right arrow over (R)}since the liquid crystal molecules may be arranged to balance the twoforces. However, the closer to the central lines C and B of the regionsNR and WR, the smaller the angle |ψ_(R)−ψ_(LC)| which the molecular axismakes with the rubbing direction {right arrow over (R)}, and themolecular axis on the central lines B and C is in the rubbing direction{right arrow over (R)}. The angle made by the optical axis of thepolarizer 5 with the molecular axis has the same distribution as theabove since the optical axis of the polarizer 5 is parallel to therubbing direction {right arrow over (R)}, and this angle is closelyrelated to the transmittance of the incident light.

[0146] On the other hand, the xy plane component of the electric field{right arrow over (E)}_(xy) becomes smaller along the z-axis as goesfrom the lower aligning film 4 to the upper aligning film 6. The elasticrestoring force generated by the aligning treatment is the greatest onthe surfaces of the aligning films 4 and 6, and it is reduced as goes tothe center of the liquid crystal layer between the aligning films 4 and6.

[0147]FIG. 14 illustrates the twist angle made by the molecular axiswith the x-axis from the lower aligning film 4 to the upper aligningfilm 6 along the z-axis. In FIG. 14, the horizontal axis indicates theheight from the lower aligning film 4, and the vertical axis representsthe twist angle, where d is the cell gap between the two aligning films4 and 6.

[0148] As illustrated in FIG. 14, the twist angle on the surfaces of thealigning films 4 and 6 is large since the aligning force of the aligningfilms 4 and 6 is great. The twist angle becomes small as goes to thecenter of the liquid crystal layer, and the molecular axis at the centerof the liquid crystal layer is substantially in the direction of theelectric field component {right arrow over (E)}_(xy). The molecular axisjust on the aligning films 4 and 6 is arranged in the rubbing direction{right arrow over (R)}.

[0149] Supposing that the difference of the twist angle between theadjacent liquid crystal molecules is called twist, the twist correspondsto the slope of the curve in FIG. 14. The twist is large near thesurfaces of the aligning films 4 and 6, and it decreases as goes to thecenter of the liquid crystal layer.

[0150]FIGS. 15, 16 and 17 illustrate the variation of the tilt anglewhich the molecular axis makes with x-axis or the initially aligneddirection on a plane perpendicular to the substrate, for example,zx-plane. FIG. 15 illustrates only the substrates 100 and 200 for thepurpose of simplifying explanation. In FIG. 15, the zx plane componentof the {right arrow over (R)} indicating the rubbing direction in FIG.12 is represented by {right arrow over (R)}_(zx) and the zx planecomponent of the electric field is represented by {right arrow over(E)}_(zx), while the angle made by the field component {right arrow over(E)}_(zx) with the x axis is indicated by θ_(E), and the tilt angle madeby the molecular axis with the x axis is indicated by θ_(LC). Here,{right arrow over (R)}_(zx) is in the x direction since the vector{right arrow over (R)} exists on the xy plane assuming a pretilt angleis ignored.

[0151] The magnitude of the field component {right arrow over (E)}_(zx)and the angle θ_(E) becomes small as goes to the upper substrate 200from the lower substrate 100.

[0152] As described above, the elastic restoring force by the aligningtreatment is the largest on the surfaces of the two substrates 100 and200, and it becomes small as goes to the center of the liquid crystallayer.

[0153] The liquid crystal molecules may be arranged to balance the twoforces As illustrated in FIG. 7, the molecular axis on the surfaces ofthe substrates 100 and 200 is arranged substantially parallel to thex-axis since the aligning force is the strongest there. Since the forcedue to the electric field becomes relatively stronger compared with thealigning force from the substrates 100 and 200 to a certain point, themagnitude of the tilt angle θ_(LC) increases continuously. Here, thevertex of the curve is formed at a point near the lower substrate 100.

[0154] On the other hand, the angle θ_(E) which the field component{right arrow over (E)}_(zx) makes with the x axis is almost zero on theboundary lines A and D, and it becomes large as goes to the central lineB-B The magnitude of the field component {right arrow over (E)}_(zx) isthe greatest on the boundary lines A and D, and it is reduced as goes tothe central line B-B.

[0155] The magnitude of the elastic restoring force by the aligningtreatment is constant on the x-axis regardless of the position.

[0156] Accordingly, as illustrated in FIG. 17, the tilt angle of theliquid crystal molecule is almost zero on the boundary lines A and D,and it decreases as goes to the central lines C and B. Therefore, thetilt angle of the liquid crystal molecules has the similar distributionsto the angle θ_(E) made by the field component {right arrow over(E)}_(zx) with the x axis, although the tilt angle varies more smoothlythan the angle θ_(E).

[0157] As described above, when the voltages are applied to the twoelectrodes 1 and 2, the liquid crystal molecules are re-arranged to havethe twist angle and the tilt angle. The transmittance of the incidentlight varies due to the variation of the twist angle and the tilt angle.On the boundary lines A and D, there is little variation in the tiltangle along the z-axis, but the twist angle varies very much. On thecentral lines B and C, on the other hand, there is little variation inthe twist angle along the z-axis but there is a little variation in thetilt angle. Accordingly, both the twist angle and the tilt angle vary inthe region between the boundary lines A and D and the central lines Band C. As a result, a transmittance curve as a function of position hasa similar shape to the lines of force.

[0158] The third embodiment uses a liquid crystal having positivedielectric anisotropy but the liquid crystal molecules it their initialstates are perpendicular to the substrates.

[0159] The structure of an LCD according to the third embodiment issimilar to the first embodiment, and thus the shape of the electricfield is similar. However, the rearrangement of the liquid crystalmolecules due to the different initial states is different from thefirst embodiment.

[0160] In the initial state, the two aligning films 4 and 6 are rubbedor exposed to ultraviolet light, and the liquid crystal molecules arealigned perpendicular to the substrates 100 and 200. The liquid crystalmolecules may have some pre-tilt angle with respect to the substrates100 and 200 but they are aligned substantially perpendicular to thesubstrates 100 and 200. When viewed on a plane parallel to thesubstrates 100 and 200, the liquid crystal molecules are arranged tohave a predetermined angle with respect to the directions parallel andperpendicular to the linear electrodes 1. The polarizing directions ofthe polarizing plates 20 and 21 are perpendicular to each other, and thepolarizing direction of the polarizer 5 almost coincides with therubbing direction. Then the initial state is black state. The liquidcrystal is nematic and may have chiral dopant of 0.001-3.0 wt %.

[0161] For simplicity, it is assumed that a direction perpendicular tothe substrates is z direction, a direction perpendicular to thesubstrates and to the direction of the linear electrodes 1 is xdirection, and a direction parallel to the direction of the linearelectrodes 1 is y direction. That is to say, it is assumed that thedirection from left to right in FIG. 1 is the positive x direction, thedirection upward along the linear electrodes 1 in FIG. 1 is the positivey direction, and the direction from the lower substrate 200 to the uppersubstrate 100 in FIG. 2 is the positive z direction.

[0162] First, the variation of a twist angle, which is defined by theangle made by the projection of the long axis of the liquid crystalmolecule with the x axis or the initially aligned direction onto xyplane parallel to the substrate 100 and 11, is described with referenceto FIGS. 18, 19 and 20.

[0163] As shown in FIG. 18, the rubbing direction is indicated by {rightarrow over (R)}, an x-y plane component of the electric field isindicated by err and the polarizing direction or the optical axis of thepolarizer 5 is indicated by {right arrow over (P)}, while the angle madeby the rubbing direction {right arrow over (R )} with the x axis isrepresented by _(ψR), and the angle made by the long axis of the liquidcrystal molecule with the x axis is represented by ψ_(LC). The angleψ_(P) made by the optical axis of the polarizer 5 with the x-axis isequal to ψ_(R) since the optical axis of the polarizer 5 is parallel tothe rubbing direction {right arrow over (R)}.

[0164] The x-y plane component {right arrow over (E)}_(xy) of theelectric field is in the positive x direction from the boundary line Ato the central line B of the wide region WR, and in the negative xdirection from the central line B of the wide region WR to the nextboundary line D.

[0165] The strength of the electric field component {right arrow over(E)} is the largest on the boundary lines A and D, and it becomessmaller as goes to the central line B-B, where the strength of theelectric field component {right arrow over (E)}_(xy) is zero.

[0166] The magnitude of the elastically restoring force generated by therubbing process is substantially constant on the xy plane regardless ofposition.

[0167] As illustrated in FIG. 19, the long axis of the liquid crystalmolecule or the molecular axis on the boundary lines A and D issubstantially parallel to the electric field component {right arrow over(E)}_(xy), and makes a large angle with respect to the rubbing direction{right arrow over (R)} since the liquid crystal molecules may bearranged to balance the two forces. However, the closer to the centrallines C and B of the regions NR and WR, the smaller the angle|ψ_(R)−ψ_(LC)| which the molecular axis makes with the rubbing direction{right arrow over (R)}, and the molecular axis on the central lines Band C is in the rubbing direction {right arrow over (R)}. The angle madeby the optical axis of the polarizer 5 with the molecular axis has thesame distribution as the above since the optical axis of the polarizer 5is parallel to the rubbing direction {right arrow over (R)}, and thisangle is closely related to the transmittance of the incident light.

[0168] On the other hand, the xy plane component of the electric field{right arrow over (E)}_(xy) becomes smaller along the z-axis as goesfrom the lower aligning film 4 to the upper aligning film 6. The elasticrestoring force generated by the aligning treatment is the greatest onthe surfaces of the aligning films 4 and 6, and it is reduced as goes tothe center of the liquid crystal layer between the aligning to films 4and 6.

[0169]FIG. 20 illustrates the twist angle made by the molecular axiswith the x-axis from the lower aligning film 4 to the upper aligningfilm 6 along the z-axis. In FIG. 20, the horizontal axis indicates theheight from the lower aligning film 4, and the vertical axis representsthe twist angle, where d is the cell gap between the two aligning films4 and 6.

[0170] As illustrated in FIG. 20, the twist angle on the surfaces of thealigning films 4 and 6 is large since the aligning force of the aligningfilms 4 and 6 is great. The twist angle becomes small as goes to thecenter of the liquid crystal layer, and the molecular axis at the centerof the liquid crystal layer is substantially in the direction of theelectric field component {right arrow over (E)}_(xy). The molecular axisjust on the aligning films 4 and 6 is arranged in the rubbing direction{right arrow over (R)}.

[0171] Supposing that the difference of the twist angle between theadjacent liquid crystal molecules is called twist, the twist correspondsto the slope of the curve in FIG. 20. The twist is large near thesurfaces of the aligning films 4 and 6, and it decreases as goes to thecenter of the liquid crystal layer.

[0172]FIGS. 21, 22 and 23 illustrate the variation of the tilt anglewhich the molecular axis makes with x-axis or the initially aligneddirection on a plane perpendicular to the substrate, for example, zxplane. FIG. 21 illustrates only the substrates 100 and 200 for thepurpose of simplifying explanation. In FIG. 21, the zx plane componentof the {right arrow over (R)} indicating the rubbing direction in FIG.18 is represented by {right arrow over (R)} and the zx plane componentof the electric field is represented by {right arrow over (E)}_(zx),while the angle made by the field component {right arrow over (E)} withthe z axis is indicated by θ_(E), and the tilt angle made by themolecular axis with the z axis is indicated by θ_(LC). Here, {rightarrow over (R)}_(zx) is in the x direction since the vector {right arrowover (R)} exists on the xy plane assuming a pretilt angle is ignored.

[0173] The magnitude of the field component {right arrow over (E)}_(zx)and the angle θ_(E) becomes large as goes to the upper substrate 200from the lower substrate 100.

[0174] As described above, the elastic restoring force by the aligningtreatment is the largest on the surfaces of the two substrates 100 and200, and it becomes small as goes to the center of the liquid crystallayer.

[0175] The liquid crystal molecules may be arranged to balance the twoforces.

[0176] As illustrated in FIG. 21, the molecular axis on the surfaces ofthe substrates 100 and 200 is arranged substantially parallel to thez-axis since the aligning force is the strongest there. Since the forcedue to the electric field becomes relatively stronger compared with thealigning force from the substrates 100 and 200 to a certain point, themagnitude of the tilt angle θ_(LC) increases continuously. Here, thevertex of the curve is formed at a point near the lower substrate 100.

[0177] On the other hand, the angle θ_(E) which the field component{right arrow over (E)}_(zx) makes with the z axis is almost 90 degreeson the boundary lines A and D, and it becomes small as goes to thecentral line B-B. The magnitude of the field component {right arrow over(E)}_(zx) is the greatest on the boundary lines A and D, and it is toreduced as goes to the central line B-B.

[0178] The magnitude of the elastic restoring force by the aligningtreatment is constant on the x-axis regardless of the position.

[0179] Accordingly, as illustrated in FIG. 23, since the long axes ofthe liquid crystal molecules at the boundary lines A and D are almostperpendicular to the field direction, the lines A and D form adiscontinuous plane. However, the tilt angle of the liquid crystalmolecule Is almost 90 degrees near the boundary lines A and D, and itdecreases as goes to the central lines C and B. Therefore, the tiltangle of the liquid crystal molecules has the similar distributions tothe angle θ_(E) made by the field component {right arrow over (E)}_(zx)with the z axis, although the tilt angle varies more smoothly than theangle θ_(E).

[0180] When the liquid crystal molecules have pre-tilt angle, thediscontinuous plane may be eliminated.

[0181] As described above, when the voltages are applied to the twoelectrodes 1 and 2, the liquid crystal molecules are re-arranged to havethe twist angle and the tilt angle. The transmittance of the incidentlight varies due to the variation of the twist angle and the tilt angle.On the boundary lines A and D, there is large variation in the tiltangle and the twist angle along the z-axis. On the central lines B andC, on the other hand, there is little variation in the twist angle andthe tilt angle along the z-axis. Accordingly, both the twist angle andthe tilt angle vary in the region between the boundary lines A and D andthe central lines B and C. As a result, a transmittance curve as afunction of position has a similar shape to the lines of force.

[0182] The fourth embodiment uses a liquid crystal having negativedielectric anisotropy and the liquid crystal molecules in their initialstates are perpendicular to the substrates.

[0183] The structure of an LCD according to the third embodiment issimilar to the first embodiment, and thus the shape of the electricfield is similar. However, the rearrangement of the liquid crystalmolecules due to the different initial states is different from thefirst embodiment.

[0184] In the initial state, the two aligning films 4 and 6 are rubbedor exposed to ultraviolet light, and the liquid crystal molecules arealigned perpendicular to the substrates 100 and 200. The liquid crystalmolecules may have some pre-tilt angle with respect to the substrates100 and 200 but they are aligned substantially perpendicular to thesubstrates 100 and 200. When viewed on a plane parallel to thesubstrates 100 and 200, the liquid crystal molecules are arranged tohave a predetermined angle with respect to the directions parallel andperpendicular to the linear electrodes 1. The polarizing directions ofthe polarizing plates 20 and 21 are perpendicular to each other, and thepolarizing direction of the polarizer 5 almost coincides with therubbing direction. Then the initial state is black state. The liquidcrystal is nematic and may have chiral dopant of 0.001-3.0 wt %.

[0185] For simplicity, it is assumed that a direction perpendicular tothe substrates is z direction, a direction perpendicular to thesubstrates and to the direction of the linear electrodes 1 is xdirection, and a direction parallel to the direction of the linearelectrodes 1 is y direction. That is to say, it is assumed that thedirection from left to right in FIG. 1 is the positive x direction, thedirection upward along the linear electrodes 1 in FIG. 1 is the positivey direction, and the direction from the lower substrate 200 to the uppersubstrate 100 in FIG. 2 is the positive z direction.

[0186] First, the variation of a twist angle, which is defined by theangle made by the projection of the long axis of the liquid crystalmolecule with the x axis or the initially aligned direction onto xyplane parallel to the substrate 100 and 11, is described with referenceto FIGS. 24, 25 and 26.

[0187] As shown in FIG. 24, the rubbing direction is indicated by {rightarrow over (R)}, an x-y plane component of the electric field isindicated by {right arrow over (E)}_(xy) , and the polarizing directionor the optical axis of the polarizer 5 is indicated by {right arrow over(P)}, while the angle made by the rubbing direction {right arrow over(R)} with the x axis is represented by 104 _(R), and the angle made bythe long axis of the liquid crystal molecule with the x axis isrepresented by ψ_(LC). The angle ψ_(P) made by the optical axis of thepolarizer 5 with the x-axis is equal to ψ_(R) since the optical axis ofthe polarizer 5 is parallel to the rubbing direction {right arrow over(R)}.

[0188] The x-y plane component {right arrow over (E)}_(xy) of theelectric field is in the positive x direction from the boundary line Ato the central line B of the wide region WR, and in, the negative xdirection from the central line B of the wide region WR to the nextboundary line D.

[0189] The strength of the electric field component {right arrow over(E)}_(xy) is the largest on the boundary lines A and D, and it becomessmaller as goes to the central line B-B, where the strength of theelectric field component {right arrow over (E)}_(xy) is zero.

[0190] The magnitude of the elastically restoring force generated by therubbing process is substantially constant on the xy plane regardless ofposition.

[0191] As illustrated in FIG. 25, the long axis of the liquid crystalmolecule or the molecular axis on the boundary lines A and D issubstantially perpendicular to the electric field component {right arrowover (E)}_(xy), and to the rubbing direction {right arrow over (R)}since the liquid crystal molecules may be arranged to balance the twoforces. However, the closer to the central lines C and B of the regionsNR and WR, the smaller the angle |ψ_(R)−ψ_(LC)| which the molecular axismakes with the rubbing direction {right arrow over (R)}, and themolecular axis on the central lines B and C is in the rubbing direction{right arrow over (R)}. The angle made by the optical axis of thepolarizer 5 with the molecular axis has the same distribution as theabove since the optical axis of the polarizer 5 is parallel to therubbing direction {right arrow over (R)}, and this angle is closelyrelated to the transmittance of the incident light.

[0192] On the other hand, the xy plane component of the electric field{right arrow over (E)}_(xy) becomes smaller along the z-axis as goesfrom the lower aligning film 4 to the upper aligning film 6. The elasticrestoring force generated by the aligning treatment is the greatest onthe surfaces of the aligning films 4 and 6, and it is reduced as goes tothe center of the liquid crystal layer between the aligning films 4 and6.

[0193]FIG. 26 illustrates the twist angle made by the molecular axiswith the x-axis from the lower aligning film 4 to the upper aligningfilm 6 along the z-axis. In FIG. 26, the horizontal axis indicates theheight from the lower aligning film 4, and the vertical axis representsthe twist angle, where d is the cell gap between the two aligning films4 and 6.

[0194] As illustrated in FIG. 26, the twist angle on the surfaces of thealigning films 4 and 6 is large since the aligning force of the aligningfilms 4 and 6 is great. The twist angle becomes small as goes to thecenter of the liquid crystal layer, and the molecular axis at the centerof the liquid crystal layer is substantially in the direction of theelectric field component {right arrow over (E)}_(xy). The molecular axisjust on the aligning films 4 and 6 is arranged in the rubbing direction{right arrow over (R)}.

[0195] Supposing that the difference of the twist angle between theadjacent liquid crystal molecules is called twist, the twist correspondsto the slope of the curve in FIG. 26. The twist is large near thesurfaces of the aligning films 4 and 6, and it decreases as goes to thecenter of the liquid crystal layer.

[0196]FIGS. 27, 28 and 29 illustrate the variation of the tilt anglewhich the molecular axis makes with x-axis or the initially aligneddirection on a plane perpendicular to the substrate, for example, zxplane. FIG. 27 illustrates only the substrates 100 and 200 for thepurpose of simplifying explanation. In FIG. 27, the zx plane componentof the {right arrow over (R)} indicating the rubbing direction in FIG.24 is represented by {right arrow over (R)}_(zx), and the zx planecomponent of the electric field is represented by {right arrow over(E)}_(zx), while the angle made by the field component {right arrow over(E)}, with the z axis is indicated by θ_(E), and the tilt angle made bythe molecular axis with the z axis is indicated by θ_(LC). Here, {rightarrow over (R)}_(zx) is in the x direction since the vector {right arrowover (R)} exists on the xy plane assuming a pretilt angle is ignored.

[0197] The magnitude of the field component {right arrow over (E)}_(zx)and the angle θ_(E) becomes large as goes to the upper substrate 200from the lower substrate 100.

[0198] As described above, the elastic restoring force by the aligningtreatment is the largest on the surfaces of the two substrates 100 and200, and it becomes small as goes to the center of the liquid crystallayer.

[0199] The liquid crystal molecules may be arranged to balance the twoforces. As illustrated in FIG. 27, the molecular axis on the surfaces ofthe substrates 100 and 200 is arranged substantially parallel to thez-axis since the aligning force is the strongest there. Since the forcedue to the electric field becomes relatively stronger compared with thealigning force from the substrates 100 and 200 to a certain point, themagnitude of the tilt angle θ_(LC) increases continuously. Here, thevertex of the curve is formed at a point near the lower substrate 100.

[0200] On the other hand, the angle θ_(E) which the field component{right arrow over (E)}_(zx) makes with the z axis is almost 90 degreeson the boundary lines A and D, and it becomes small as goes to thecentral line B-B. The magnitude of the field component {right arrow over(E)}_(zx) is the greatest on the boundary lines A and D, and it isreduced as goes to the central line B-B.

[0201] The magnitude of the elastic restoring force by the aligningtreatment is constant on the x-axis regardless of the position.

[0202] Accordingly, as illustrated in FIG. 29, the tilt angle of theliquid crystal molecule is almost zero degrees on the boundary lines Aand D, and it increases as goes to the central lines C and B. Therefore,the tilt angle of the liquid crystal molecules has the similardistributions to the angle θ_(E) made by the field component {rightarrow over (E)}_(zx) with the z axis, although the tilt angle variesmore smoothly than the angle θ_(E).

[0203] When the liquid crystal molecules have pre-tilt angle, thediscontinuous plane may be eliminated.

[0204] As described above, when the voltages are applied to the twoelectrodes 1 and 2, the liquid crystal molecules are re-arranged to havethe twist angle and the tilt angle. The transmittance of the incidentlight varies due to the variation of the twist angle and the tilt angle.On the boundary lines A and D, there is little variation in the tiltangle but the twist angle along the z-axis varies greatly. On thecentral lines B and C, on the other hand, there is little variation inthe twist angle along the z-axis but there is a little variation in thetilt angle. Accordingly, both the twist angle and the tilt angle vary inthe region between the boundary lines A and D and the central lines Band C. As a result, a transmittance curve as a function of position hasa similar shape to the lines of force.

[0205] Next, modifications of the structure of the electrodes aredescribed.

[0206] The LCD according to the fifth embodiment of the presentinvention is described with reference to the FIGS. 30 and 31.

[0207] Unlike the first to fourth embodiments of the present invention,the portions of the planar electrode overlapping the linear electrodesare removed in this embodiment. Therefore, the planar electrode isdivided into a pluraltity of common electrodes 200, each being locatedbetween the linear electrodes 1 Furthermore, since the two adjacentcommon electrodes 20in the transverse direction should be connected,there are provided common electrode lines or connections 23 connectingthe common electrodes 200. These connections 23 may overlap the linearelectrodes 1 as shown in FIG. 30, but may be located outward the linearelectrodes 1 in order to preventing overlapping. In FIG. 30, openings 8are defined by the adjacent two common electrodes 20and the connections23 connecting them.

[0208] For simplicity, a region on a linear electrode 1 is defined as anarrow region NR, a region including an opening 8 and connections 23 asa boundary region BR, and a region on the common electrode 20as a wideregion WR, while the widths of the narrow region NR, the boundary regionBR, and the wide region WR is designated as a, c and b, respectively.

[0209] In FIG. 31 which is a cross-sectional view taken along line V-V′in FIG. 30, the lines of force between the central line C of the narrowregion NR and the central line B of the wide region WR are in parabolicor semi-elliptical shapes. When the width of the boundary region BR isfixed, the location of the vertex of the line of force varies dependingon the value of the a/b. However, the vertex of the parabolic line offorce is located approximately on the central line I of the boundaryregion BR. The shape of the parabola is asymmetric when a is differentfrom b, but it is substantially symmetric when a and b are the same.When c is zero, the electric field has the shape similar to the electricfield of the first embodiment, and even though c is not zero, theelectric field on the planar electrode 2 or the linear electrodes 1 alsohas the horizontal component and the vertical component.

[0210] Accordingly, in the transmissive type display where both oreither of the two electrodes 1 and 2 is made of transparent material,the light incident on the liquid crystal layer through the transparentelectrode 1 or 2 is controlled by the twist and the tilt of the liquidcrystal molecules on the transparent electrode. Here, the smaller thevalue of c, the lesser the threshold voltage of the liquid crystalmaterial.

[0211] In case of the reflection type display where the two electrodes 1and 2 are made of opaque metal having high reflectance such as Al, thereflectance is high as the value of c is small. In this case, there-arranged liquid crystal molecules on the electrodes 1 and 2 havingthe twist angle and the tilt angle change the polarization of the lightincident on the liquid crystal layer through the upper substrate andthat of the light which is reflected by the electrodes 1 and 2 andincident on the liquid crystal layer.

[0212] The LCD according to the sixth embodiment of the presentinvention having a thin film transistor as a switching element as wellas the electrodes suggested in the first to the fifth embodiments, isdescribed in detail with reference to FIGS. 32 to 34.

[0213]FIG. 32 is a layout of a pixel formed on the lower substrate ofthe LCD according to the sixth embodiment of the present invention,wherein hundreds of thousands of such pixels are formed in a matrix typein the LCA.

[0214] A plurality of gate lines or scanning signal lines 10 and aplurality of planar common electrodes 20 are formed on a transparentinsulating substrate 100. The scanning signal lines to are elongated inthe transverse direction, and the common electrodes are located betweenthe scanning signal lines 10. A portion 11 of the scanning signal line10 serve as a gate electrode, and connections 23 connect adjacent commonelectrodes 20.

[0215] The scanning signal lines 10 and the common electrodes 20 arecovered with a gate insulating film 40, and a channel layer 51 made ofamorphous silicon is formed on a portion of a gate insulating film 40opposite the gate electrode 11 of the scanning signal line 10. Twoseparated portions 61 and 62 of the doped amorphous silicon layerheavily doped with n-type impurity are formed on portions of the channellayer 51, and the portions 61 and 62 are opposite each other withrespect to the gate electrode 11.

[0216] On the other hand, a plurality of data lines 70 are formed on thegate insulating film 40 and elongated longitudinally to intersect thegate lines 10. A branch of the data line 70 extends to one portion 61 ofthe doped amorphous silicon layer to form a source electrode 71, and adrain electrode 72 is formed on the other portion 62 of the dopedamorphous silicon layer. The gate electrode 11, the source electrode 71and the drain electrode 72 form electrodes of the TFT along with thechannel layer 51. The doped amorphous silicon layer 61 and 62 improvesohmic contact between the source and the drain electrode 71 and 72 andthe amorphous silicon layer 51.

[0217] The drain electrode 72 extends to form a plurality of linearpixel electrodes 75 elongated longitudinally and a connecting portion 76of the pixel electrodes 75. The data line 70, the source and the drainelectrodes 71 and 72 and the connecting portion 76 are covered with apassivation film 80, and the aligning film 4 is coated thereon.

[0218] Since the connections 23 overlap the data line 70, and theoverlapping causes parasitic capacitance to increase the RC delay of theimage signal of the data line 70. To reduce the RC delay, it ispreferable that the overlapping between the connection 23 and the dataline 70 is minimized.

[0219] A portion of the passivation film 80 in the display region wherethe pixel electrode 75 and the common electrode 20 are located may beremoved to obtain sufficient electric field.

[0220] Other amorphous silicon patterns 52 are formed on the portions ofthe gate insulating layer 3 where the gate lines 10, the connections 23intersect the data lines 70 in order to enhance the insulationtherebetween.

[0221] A method for manufacturing the LCD according to the sixthembodiment of the present invention is described in detail hereinafter.

[0222] First, a transparent conductive layer such as indium tin oxide(ITO) is deposited and patterned to form common electrodes 20 and theirconnections 23. A film made of Cr. Al, Mo, Ti, Ta or their alloys aredeposited and patterned to form scanning signal lines 10. A gateinsulating film 40 made of such as silicon nitride is deposited to coverthe common electrode 20, the gate electrode 11 and the scanning signallines 10. An amorphous silicon layer and an n+ type amorphous siliconlayer are sequentially deposited on the gate insulating film 40, andpatterned to form the patterns 51, 52 and 60. A film made of Cr, Al, Moand Ta or their alloys are deposited and patterned to form a data wireincluding data lines 70, source electrodes 71, drain electrodes 72 andpixel electrodes 75. A portion of the n+ type amorphous silicon layerwhich is not covered by the data wire are removed. Next, a passivationfilm 80 is deposited and patterned to form an opening 81 on the displayregion. Finally, an aligning film 4 is coated thereon.

[0223] Next, a substrate for a liquid crystal display and amanufacturing method thereof according to the seventh embodiment aredescribed in detail.

[0224] First, the structure of a liquid crystal display substrate isdescribed with reference to FIGS. 35A to 35C. FIG. 35A is a layout viewof a lower substrate of a liquid crystal display, and FIGS. 35B and 35Care sectional views taken along the lines VII1B-VII1B′ and VII1C-VII1C′respectively.

[0225] As shown in FIGS. 35A to 35C, a planar common electrode 20 madeof transparent conductive material such as ITO (indium tin oxide) isformed on a transparent insulating substrate 100. The common electrode20 is in a pixel region, and is connected to adjacent common electrodes(not shown) in adjacent pixel regions via a plurality of connections 23on the substrate 100 to transmit common signals. A common signaltransmitter 24 on the substrate 100 is electrically connected to thecommon electrode 20 via the connection 23, and located near the rightedge of the substrate 100.

[0226] At the lower part of the pixel region, a gate line 10 is formedon the substrate 100 and extends in the transverse direction. The gateline 10 is connected to a gate pad 12 which is located near the leftedge of the substrate 100 and receives external scanning signals. Aportion 11 of the gate line 10 serves as a gate electrode.

[0227] The common electrode 20, the connections 23, the common signaltransmitter 24, the gate line 10 and the gate pad 12 are made oftransparent conductive materials, and a redundant pattern for preventingtheir disconnection is formed on the upper part of the common electrode20, the connections 23, the common signal transmitter 24 and the gateline 10. A redundant connection 33 is provided on the connections 23 andupper part of the common electrode 20, a redundant common signaltransmitter 34 on the common signal transmitter 24, and a redundant gateline 30 and a redundant gate electrode 31 on the gate line 10 and thegate electrode 11, respectively. The redundant pattern 30, 31, 33 and 34may be made of any conductive material such as Al or Al alloy. However,when using Al or Al alloy, since direct contact of ITO and Al and Alalloy yields an oxide therebetween, a buffer layer 32 and 35 made ofrefractory metal such as Cr or MoW alloy is interposed between the twolayers.

[0228] The common electrode 20 and the redundant pattern are coveredwith a gate insulating layer 40. As shown in FIGS. 35A and 35B, achannel layer 51 made of amorphous silicon is formed on the gateinsulating layer 40 opposite the gate electrode 11. Two separateportions 61 and 62 of a contact layer made of doped amorphous siliconheavily doped with n type impurity are formed on the channel layer 51and located opposite each other with respect to the gate electrode 11.

[0229] A data line 70 extending in the longitudinal direction is alsoformed on the gate insulating layer 40 and intersects the gate line Abranch of the data line 70 extends to one portion 61 of the dopedamorphous silicon layer to form a source electrode 71, and a drainelectrode 72 is formed on the other portion 62 of the doped amorphoussilicon layer. The gate electrode 11, the source electrode 71 and thedrain electrode 72 form electrodes of the TFT along with the channellayer 51. The doped amorphous silicon layer 61 and 62 improves ohmiccontact between the source and the drain electrodes 71 and 72 and theamorphous silicon layer 51.

[0230] The drain electrode 72 extends to form a plurality of linearpixel electrodes 75 elongated longitudinally and a connecting portion 76of the pixel electrodes 75. The data line 70, the source and the drainelectrodes 71 and 72 and the connecting portion 76 are covered with apassivation film 80, and the passivation film 80 and the gate insulatinglayer 40 having a contact hole 82 exposing the gate pad 12.

[0231] A portion of the passivation film 80 in the pixel region wherethe pixel electrode 75 and the common electrode 20 are located may beremoved to obtain sufficient electric field.

[0232] A method for manufacturing the LCD according to the seventhembodiment of the present invention is described in detail withreference to FIGS. 36A to 39C. FIGS. 36A, 37A, 38A and 39A are layoutviews of the intermediate structures of the liquid crystal displaysubstrate according to this embodiment, and FIGS. 36B and 36C, 37B and37C, 38B and 38C, and 39B and 39C are sectional views taken along thelines VII2B and VII2C in FIG. 36A, VII3B and VII3C in FIG. 37A, andVII3B and VII3C in FIG. 38A and VII4B and VII4C in FIG. 39A.

[0233] First, as shown in FIGS. 36A-36C, a transparent conductive layersuch as indium tin oxide is deposited to the thickness of 50-100 nm onan insulating substrate 100 and patterned using a first mask to form acommon wire including a common electrode 20, their connections 23 and acommon signal transmitter 24, and a gate wire including a gate line 10and a gate pad 12.

[0234] As shown in FIGS. 37A-37C, a lower conductive film made of arefractory metal such as Cr or Mo-W, and an upper conductive film of Alor Al alloys with thickness of 100-400 nm are deposited in sequence andpatterned by using a second mask to form a redundant pattern 30, 33 and34 and a buffer layer 32 and 35 thereunder. A gate insulating layer 40is deposited thereon.

[0235] As shown in FIGS. 38A-38C, an amorphous silicon layer and an n+type amorphous silicon layer are sequentially deposited on the gateinsulating film 40, and patterned by using a third mask to form thepatterns 51 and 60.

[0236] As shown in FIGS. 39A-39C, a film made of Cr, Al, Mo and Ta ortheir alloys are deposited to a thickness of 100-200 nm and patterned byusing a fourth mask to form a data wire including data lines 70, sourceelectrodes 71, drain electrodes 72 and pixel electrodes 75. A portion ofthe n+ type amorphous silicon layer which is not covered by the datawire are removed.

[0237] Finally, a passivation film 80 with thickness of 200-400 nm isdeposited and patterned along with the gate insulating layer 40 by usinga fifth mask to form a contact hole 82.

[0238] Alternatively, the common wire and the gate wire are formed afterthe redundant pattern and the buffer layer is formed.

[0239] The material and the width of the electrodes 20 and 75 and thedistance between the electrodes 20 may vary depending on the design ofthe liquid crystal display. For example, if the pixel electrodes 57 aretransparent, the liquid crystal molecules over the pixel electrodes 57contribute to the display of images, causing larger transmittance. Incase of reflective liquid crystal display, the common electrode 20 andthe pixel electrodes 75 may be made of an opaque material having largereflectance.

[0240] Next, a substrate for a liquid crystal display and amanufacturing method thereof according to the eighth embodiment aredescribed in detail.

[0241] The structure of a liquid crystal display substrate withreference to FIGS. 40 to 42. FIG. 40 is a layout view of a lowersubstrate of a liquid crystal display, and FIGS. 41 and 42 are differentsectional views taken along the line VIIIA-VIIIA′.

[0242] As shown in FIGS. 40 to 42, a plurality of rectangular commonelectrodes 20 made of transparent conductive material such as ITO(indium tin oxide) are formed on a transparent insulating substrate 100.Each common electrode 20 is in a pixel region, and is connected toadjacent common electrodes in adjacent pixel regions via a plurality ofconnections 23 on the substrate 100 to transmit common signals. However,the connections 23 may be eliminated.

[0243] A plurality of common electrode lines 33 located at the upperparts of the common electrodes 20 extends in the transverse direction toelectrically connect the common electrodes 20. The common electrodelines 33 have lower resistivity than the common electrodes 20, and arelocated either on the common electrodes 20 as in FIG. 41 or under thecommon electrodes 20 as in FIG. 42.

[0244] Between the common electrodes 20 adjacent along a column, a gateline 10 is formed on the substrate 100 and extends in the transversedirection. A portion 11 of the gate line 10 serves as a gate electrode.

[0245] The common electrode lines 33 and the gate line 10 may be made ofany conductive material such as Al, Al alloy, Mo or Cr. However, whenusing Al or Al alloy, since direct contact of ITO and Al and Al alloyyields an oxide therebetween, a buffer layer made of refractory metalsuch as Cr or MoW alloy is interposed between the two layers.

[0246] The common electrodes 20 and the gate line 10 and the commonelectrode lines 33 covered with a gate insulating layer 40. As shown inFIGS. 41 and 42, a channel layer 51 made of amorphous silicon is formedon the gate insulating layer 40 opposite the gate electrode 11. Twoseparate portions 61 and 62 of a contact layer made of doped amorphoussilicon heavily doped with n type impurity are formed on the channellayer 51 and located opposite each other with respect to the gateelectrode 11.

[0247] A data line 70 extending in the longitudinal direction is alsoformed on the gate insulating layer 40 and intersects the gate line 10.A branch of the data line 70 extends to one portion 61 of the dopedamorphous silicon layer to form a source electrode 71, and a drainelectrode 72 is formed on the other portion 62 of the doped amorphoussilicon layer. The gate electrode 11, the source electrode 71 and thedrain electrode 72 form electrodes of the TFT along with the channellayer 51. The doped amorphous silicon layer 61 and 62 improves ohmiccontact between the source and the drain electrodes 71 and 72 and theamorphous silicon layer 51.

[0248] The drain electrode 72 extends to form a plurality of linearpixel electrodes 75 elongated longitudinally and a connecting portion 76of the pixel electrodes 75. The data line 70, the source and the drainelectrodes 71 and 72 and the connecting portion 76 are covered with apassivation film 80.

[0249] A plurality of isolated amorphous silicon patterns 52 are locatedat the intersections of the gate line 10 and the common electrode lines33 and the data lines 70, and interposed between the gate insulatinglayer 40 and the data lines 70.

[0250] A method for manufacturing the LCD according to the eighthembodiment of the present invention is described.

[0251] In the case of the structure shown in FIG. 41, an ITO layer and ametal layer are deposited in sequence. The metal layer is patterned toform common electrode lines 33 and gate lines 10, and the ITO layer ispatterned to form common electrodes 20 and connections 23.

[0252] On the other hand, in the case of the structure shown in FIG. 42,a metal layer is deposited and patterned to form common electrode lines33 and gate lines 10. Thereafter, an ITO layer is deposited andpatterned to form common electrodes 20 and connections 23. In this case,the connections 23 may be eliminated.

[0253] Next, a gate insulating layer 40, an amorphous silicon layer 51and a doped amorphous silicon layer 61 and 62 are deposited in sequence,and the doped amorphous silicon layer and the amorphous silicon layerare then patterned.

[0254] A metal film is deposited and patterned to form a data wireincluding data lines 70, source electrodes 71, drain electrodes 72 andpixel electrodes 75. A portion of the n+ type amorphous silicon layerwhich is not covered by the data wire are removed.

[0255] Finally, a passivation film 80 is deposited and patterned alongwith the gate insulating layer 40 to expose pads of the gate lines 10and of the data lines 70.

[0256] In this embodiment, since the common electrodes 20 are patternedby using the common electrode lines 33 and the gate lines 10,misalignment may be reduced.

[0257]FIG. 43 shows a sectional view taken along the line VIIIB-VIIIB′in FIG. 40 but includes upper substrate. Among the regions between thepixel electrodes 75 and the common electrodes 20, the regions S adjacentto the data line 70 have disturbed electric field due to the signalsflowing through the data line 70. Accordingly, the liquid crystalmolecules in the regions S arrange themselves different from the otherregions, and light leakage may be generated.

[0258] The ninth embodiment suggests the structure reducing the lightleakage.

[0259]FIGS. 44, 45 and 46 are sectional views of the liquid crystaldisplay according to the ninth embodiment of the present invention.

[0260] As shown in FIG. 44, a light blocking film 210 made of opaquematerial such as Cr is formed on the upper substrate 200, and located atthe position corresponding to the regions S.

[0261] In addition to the light blocking film 210 on the upper substrate200, another light blocking film 110 is formed between the data line 70and the pixel electrodes 70 adjacent thereto as shown in FIG. 45. Thelight blocking films 110 are formed on both the lower substrate 100 andthe common electrodes 20, covered with the gate insulating layer 40, andoverlap the data line 70.

[0262] It is preferable that the light blocking films 110 are conductiveas well as opaque to have a potential equal to the common electrodes 20.In this case, the light blocking films 110 block the electric field dueto the data line 70 as well as prevent light leakage in the region S.

[0263]FIG. 46 shows the structure having only light blocking film 120 onthe lower substrate 100. The light blocking film 120 is formed on thegate insulating layer 40 and covers the data line 70 at all and thepixel electrodes in part. The light blocking film 120 in FIG. 46 is madeof insulating material, preferably organic material, since it directlycontacts the data line 70 and the pixel electrodes 75.

[0264] The structures in the previous embodiments include a planarelectrode, an insulating layer covering the planar electrode and aplurality of linear electrodes on the insulating layer. However, thelinear electrode may be located under the planar electrode or may lie inthe same plane. These structures are obtained by patterning the planarelectrodes such that the planar electrode forms a continuous planebetween the linear electrodes. The planar electrode may overlap thelinear electrode in part. Otherwise, the planar electrode may notoverlap the linear electrode but the distance between the adjacentboundaries of the pixel electrode and of the linear electrode is veryclose. The width of the planar electrode is either equal to or largerthan that of the linear electrode. The liquid crystal molecules abovethe planar electrode are used for display, while the conventional IPSLCD uses the liquid crystal molecules only above the regions between theelectrodes.

[0265]FIG. 47 is a sectional view of an LCD according to the tenthembodiment of the present invention.

[0266] As shown in FIG. 10, a plurality of linear first electrodes 1 areformed on an insulating substrate 100, and the first electrodes 1 arecovered with an insulating layer 3. A plurality of planar secondelectrodes 2 are formed on the insulating layer 3, overlap the firstelectrode in part, and have the width equal to or larger than that ofthe first electrode. The first and the second electrodes 1 and 2 may betransparent or opaque according to the type of the LCD.

[0267]FIGS. 48, 49 and 50 shows an electric field, transmittance andviewing angle characteristic of the LCD according to the tenthembodiment, respectively.

[0268] When applying 0 V and 5 V to the first and the second electrodes1 and 2 respectively, the potential difference between the first and thesecond electrodes 1 and 2 yields the electric field shown in FIG. 48. InFIG. 48, solid lines indicate equipotential lines, and dotted linesindicate the lines of electrical force.

[0269] As shown in FIG. 48, the shape of the electrical field issymmetrical with respect to the central lines of the first and thesecond electrodes 1 and 2, and similar to that shown in FIG. 2.

[0270]FIG. 49 illustrates the transmittance as a function of the appliedvoltage according this embodiment. As shown in FIG. 10, the thresholdvoltage is about 1.5 V, and the saturation voltage is about 5 V.

[0271]FIG. 50 is a graphical illustration showing the viewing anglecharacteristics according to this embodiment. As shown in FIG. 50, theboundary of the region where the contrast is equal to or more than 10 issubstantially over 60 degrees.

[0272] The LCD according to a eleventh embodiment of the presentinvention having a thin film transistor as a switching element as wellas the electrodes suggested in the tenth embodiment, is described indetail with reference to FIGS. 51 to 53.

[0273]FIG. 51 is a layout of a lower substrate of an LCD according tothe eleventh embodiment of the present invention, wherein hundreds ofthousands of such pixels are formed in a matrix type in the LCD. FIGS.52 and 53 ale sectional views Taken along the lines XIA-XIA′ andXIB-XIB′, respectively.

[0274] A plurality of gate lines or scanning signal lines 10 and a gatepad 12 are formed on a transparent insulating substrate 100. The gateline 10 extends in the transverse direction and the gate pad 12 isconnected to the left end of the gate line 10. A portion 11 of the gateline 10 serves as a gate electrode of a thin film transistor.

[0275] A plurality of common electrodes 20 elongated longitudinally areformed on the 100, and lies between the gate lines 10. A pair oftransverse common electrode lines 23 connecting the common electrodes 20are also formed on the substrate 100.

[0276] The gate lines 10, the common electrodes 20 and the commonelectrode lines 23 are covered with a gate insulating film 40, and achannel layer 51 made of amorphous silicon is formed on a portion of agate insulating film 40 opposite the gate electrode 11 of the scanningsignal line 10. Two separated portions 61 and 62 of the doped amorphoussilicon layer heavily doped with n-type impurity are formed on portionsof the channel layer 51, and the portions 61 and 62 are opposite eachother with respect to the gate electrode 11.

[0277] On the other hand, a plurality of data lines 70 and a data pad 73are formed on the gate insulating film 40. The data line 70 is elongatedlongitudinally to intersect the gate lines 10, and the data pad 73 isconnected to the upper end of the gate line 10. A branch of the dataline 70 extends to one portion 61 of the doped amorphous silicon layerto form a source electrode 71, and a drain electrode 72 is formed on theother portion 62 of the doped amorphous silicon layer. The gateelectrode 11, the source electrode 71 and the drain electrode 72 formelectrodes of the TFT along with the channel layer 51. The dopedamorphous silicon layer 61 and 62 improves ohmic contact between thesource and the drain electrodes 71 and 72 and the amorphous siliconlayer 51.

[0278] The data line 70, the data pad 73 and the source and the drainelectrodes 71 and 72 are covered with a passivation film 80. Thepassivation film 80 has contact holes 82, 83 and 84 exposing the gatepad 12, the data pad 73 and the drain electrode 84.

[0279] A plurality of linear pixel electrodes 91 elongatedlongitudinally and a connecting portion 92 of the pixel electrodes 91are formed on the passivation film 80, and a redundant gate pad 95 and aredundant data pad 96 are also formed on the passivation layer 80. Theboundaries 93 of the pixel electrodes 91 are over the common electrodes20, and the connecting portion 92 is connected to the pixel electrodes91 and connected to the drain electrode 72 through the contact hole 84.The width of the pixel electrode 91 is equal to or larger than that ofthe common electrode 20. The redundant gate pad 95 and the redundantdata pad 96 are connected to the gate pad 12 and the data pad 73 throughthe contact holes 82 and 83, respectively.

[0280] A method for manufacturing the LCD according to the eleventhembodiment of the present invention is described in detail withreference to FIGS. 51 to 53 and 54A to 57B.

[0281] First, as shown in FIGS. 54A-54B, a conductive layer made of arefractory metal such as Cr, Al, Mo, Ti, Ta or their alloys is depositedon an insulating substrate 100 and patterned using a first mask to forma common wire including a plurality of common electrodes 20 and commonelectrode lines 33, and a gate wire including a gate line 10 and a gatepad 12.

[0282] As shown in FIGS. 55A-55B, a gate insulating layer 40 of such assilicon nitride, an amorphous silicon layer and an n+ type amorphoussilicon layer are sequentially deposited on the gate insulating film 40.The n+ type amorphous silicon layer and the amorphous silicon layer arepatterned using a second mask to form the channel layer 51 and a pattern60.

[0283] As shown in FIGS. 56A-56B, a film made of Cr, Al, Mo and Ta ortheir alloys are deposited and patterned by using a third mask to form adata wire including data lines 70, a data pad 73, a source electrode 71and a drain electrodes 72. A portion of the n+ type amorphous siliconlayer which is not covered by the data wire is removed.

[0284] A passivation film 80 with thickness of 200-400 nm is depositedand patterned along with the gate insulting layer 40 by using a fourthmask to form contact holes 82. 83 and 84.

[0285] Finally, an ITO layer is deposited and patterned by using a fifthmask to form pixel electrodes 91, connecting members 92, a redundantgate pad 95 and a redundant data pad 96.

[0286] An LCD according to a twelfth embodiment has pixel electrodesdirectly on a gate insulating layer, as shown in the layout of FIG. 58.FIGS. 59 and 60 are sectional views taken along the lines XIIA-XIIA′ andXIIB-XIIB′, respectively.

[0287] A plurality of pixel electrodes 91 are formed on a portion of agate insulating layer 40 between common electrodes 20 on an insulatingsubstrate 100. A drain electrode 72 on the gate insulating layer 40extends to connecting portion 92 of the pixel electrodes 91 and iselectrically connected to the pixel electrodes 91. A passivation film 80covers a data line 70, a source electrode 71 and the drain electrode 72on the gate insulating layer 40, and has an opening 81 in the displayregion in order to obtain sufficient electrical field.

[0288] A portion of the gate insulating layer 40 on a gate pad 12connected to a gate line is removed to form a contact hole 41, and aredundant gate pad 95 on the gate insulating layer 40 is in contact withthe gate pad through the contact hole 41. A data pad 96 is formed on thegate insulating layer 40 and the data line 70 extends to the data pad 96to contact the data pad 96. The passivation layer 80 has contact holes82 and 83 respectively exposing the redundant gate pad 95 and the datapad 96.

[0289] The remaining structure is substantially the same as the eleventhembodiment.

[0290] A method for manufacturing the LCD according to the twelfthembodiment of the present invention is described in detail withreference to FIGS. 58 to 60 and 61A to 63B.

[0291] Gate lines 10, a gate pad 12, common electrodes 91 and commonelectrode lines 23 are formed, a gate insulating layer 40, an amorphoussilicon layer and a doped amorphous silicon layer are deposited, and thedoped amorphous silicon layer 51 and the amorphous silicon layer 60 arepatterned as in the eleventh embodiment.

[0292] As shown in FIGS. 61A and 61B, the gate insulating layer 40 ispatterned to form a contact hole 32 exposing the gate pad 12 by using athird mask.

[0293] As shown in FIGS. 62A and 62B, an ITO layer is deposited andpatterned by using a fourth mask to form pixel electrodes 91, connectingmembers 92, a redundant gate pad 95 and a data pad 96.

[0294] As shown in FIGS. 63A and 63B, a film made of Cr. Al, Mo and Taor their alloys are deposited and patterned by using a fifth mask toform a data wire including data lines 70, a source electrode 71 and adrain electrodes 72. A portion of the n+ type amorphous silicon layerwhich is not covered by the data wire is removed to form a contact layer61 and 62.

[0295] A passivation film 80 with thickness of 200-400 nm is depositedand patterned by using a sixth mask to form contact holes 82 and 83 andan opening 81.

[0296] As described above, the method according to the twelfthembodiment requires six masks. However, if eliminating the redundantgate pad, only 5 masks are necessary.

[0297] The step of forming the pixel electrodes and the step of formingthe data wire in the twelfth embodiment are exchanged in a thirteenthembodiment. FIG. 64 is a layout view of an LCD according to thethirteenth embodiment of the present invention, and FIGS. 65 and 66 aresectional views taken along the lines XIIIA-XIIIA′ and XIIIB-XIIIB′,respectively.

[0298] The structure of the LCD in this embodiment is substantially thesame as that in the twelfth embodiment except the points that aconnecting portion 92 is on a drain electrode 72 not under the drainelectrode 72, a data pad 73 is made of the same layer as a data line 70,and a redundant data pad 96 is on the data pad 73.

[0299] A method for manufacturing the LCD according to the thirteenthembodiment of the present invention is substantially the same as that ofthe twelfth embodiment until the step of forming contact hole 32 in agate insulating layer 40.

[0300] As shown in FIGS. 67A and 67B, a film made of Cr, Al, Mo and Taor their alloys are deposited and patterned by using a fourth mask toform a data wire including data lines 70, a source electrode 71 and adrain electrodes 72. A portion of the n+ type amorphous silicon layerwhich is not covered by the data wire is removed to form a contact layer61 and 62.

[0301] As shown in FIGS. 68A and 68B, an ITO Layer is deposited andpatterned by using a fifth mask to form pixel electrodes 91, connectingmembers 92, a redundant gate pad 95 and a data pad 96.

[0302] The step of forming a passivation layer is also the same as thetwelfth embodiment.

[0303] The fourteenth embodiment suggests a structure havingnon-overlapping electrodes.

[0304]FIG. 69 is a sectional view of an LCD according to the fourteenthembodiment of the present invention.

[0305] As shown in FIG. 69, a plurality of linear first electrodes 1 areformed on an insulating substrate 100, and the first electrodes 1 arecovered with an insulating layer 3. A plurality of planar secondelectrodes 2 are formed on the insulating layer 3, and have the widthequal to or larger than that of the first electrode. The first and thesecond electrodes 1 and 2 do not overlap each other, but the distancetherebetween is very small.

[0306] The LCD according to a fifteenth embodiment of the presentinvention having a thin film transistor as a switching element as wellas the electrode suggested in the fourteenth embodiment, is described indetail with reference to FIGS. 70 to 72.

[0307]FIG. 70 is a layout of a lower substrate of an LCD according tothe fifteenth embodiment of the present invention, and FIGS. 71 and 72are sectional views taken along the lines XVA-XVA′ and XVB-XVB′,respectively.

[0308] Pixel electrodes 91 and common electrodes 20 do not overlap, butthe distance therebetween is very small. The remaining structure issubstantially the same as the eleventh embodiment. The manufacturingmethod is similar to that of the eleventh embodiment, and itsmodifications as in the twelfth and the thirteenth are possible.

[0309] The sixteenth embodiment suggests electrodes lying on the samelayer.

[0310]FIG. 73 is a sectional view of an LCD according to the sixteenthembodiment of the present invention.

[0311] As shown in FIG. 73, a plurality of linear first electrodes 1 areformed on an insulating substrate 100, and a plurality of planar secondelectrodes 2 are formed on the substrate 100 and located between thefirst electrodes 1. The first and the second electrodes 1 and 2 do notoverlap each other, and the electric field is similar to that of thefirst embodiment.

[0312] The LCD according to a seventeenth embodiment of the presentinvention having a thin film transistor as a switching element as wellas the electrode suggested in the fourteenth embodiment, is described indetail with reference to FIGS. 74 to 76.

[0313]FIG. 74 is a layout of a lower substrate of an LCD according tothe fifteenth embodiment of the present invention, and FIGS. 75 and 76are sectional views taken along the lines XVIIA-XVIIA′ and XVIIB-XVIIB′,respectively.

[0314] A portion of a gate insulating layer 40 in the pixel regionsurrounded by gate lines 10 and data lines 70 is removed, and pixelelectrodes 91 lie between the common electrodes 20. The remainingstructure is substantially the same as the fourteenth embodiment. Themanufacturing method is similar to that of the eleventh embodiment, andits modifications as in the twelfth and the thirteenth are possible.

[0315] The fourteenth embodiment suggests a structure havingnon-overlapping electrodes.

[0316]FIG. 69 is a sectional view of an LCD according to the fourteenthembodiment of the present invention.

[0317] As shown in FIG. 69, a plurality of linear first electrodes 1 areformed on an insulating substrate 100, and the first electrodes 1 arecovered with an insulating layer 3. A plurality of planar secondelectrodes 2 are formed on the insulating layer 3, and have the widthequal to or larger than that of the first electrode. The first and thesecond electrodes 1 and 2 do not overlap each other, but the distancetherebetween is very small.

[0318] The LCD according to a fifteenth embodiment of the presentinvention having a thin film transistor as a switching element as wellas the electrode suggested in the fourteenth embodiment, is described indetail with reference to FIGS. 70 to 72.

[0319]FIG. 70 is a layout of a lower substrate of an LCD according tothe fifteenth embodiment of the present invention, and FIGS. 71 and 72are sectional views taken along the lines XVA-XVA′ and XVB-XVB′,respectively. Pixel electrodes 91 and common electrodes 20 do notoverlap, but the distance therebetween is very small. The remainingstructure is substantially the same as the eleventh embodiment. Themanufacturing method is similar to that of the eleventh embodiment, andits modifications as in the twelfth and the thirteenth are possible.

[0320] Now, embodiments having electrodes on the upper substrate as wellas those on the lower substrate will be described.

[0321] In the eighteenth embodiment, a planar electrode 2 is formed on alower substrate 100 and covered with an insulating layer 3 as shown inFIG. 77. A plurality of linear electrodes 1 made of Cr or ITO are formedon the insulating layer 3. An upper electrode 250 is formed on an uppersubstrate 200. Since field strength is stronger, the response timebecomes short and the arrangement of the liquid crystal molecules isstable. Moreover, since the upper electrode 250 has an aperture 251causing fringe field, the arrangement of the liquid crystal moleculesvaries depending on the domains.

[0322] The planar and the linear electrodes 2 and 1 according to theninth embodiment lie on the sane plane as shown in FIG. 78 and 79, and,in this case, the upper electrode 250 according to the twentiethembodiment has an aperture 251 as shown in FIG. 79.

[0323] In the meantime, as shown in the graph shown in FIG. 10, thetransmittance for the red and the green pixels is about 0.1 and that forthe blue pixels is about 0.08 which is lower than the red and the greenpixels by 20%. In order to reduce this difference between thetransmittance for respective pixels, the aperture ratio may be adjusteddepending on the color.

[0324]FIG. 80 shows a plan view of a black matrix for an LCD accordingto the twenty-first embodiment. In FIG. 80, the reference numeral 210represents a black matrix which may be formed either on an uppersubstrate or on the lower substrate, and R, G and B indicates the red,the green and the blue pixels respectively- The area of the openings isdetermined by the relation TR*YR=TG*SG=TB*SB where TR, TG and TB aretransmittances for red, green and blue pixels and SR, SG and SB are thearea of the openings for red, green and blue pixels. As a result, theaperture ratio increases as the transmittance decreases.

[0325] As described above, the viewing angle can be widened, the drivingvoltage can be lowered down, and the aperture ratio can be increased.

[0326] Other embodiments of the invention will be apparent to theskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with the true scope andspirit of the invention being indicated by the following claims.

What is claimed is:
 1. A liquid crystal display having a plurality ofpixels, comprising: first and second substrates facing each other; aplurality of first electrodes formed on the first substrate; and asecond electrode on the first substrate, the second electrode beinginsulated from the first electrodes, overlapping the first electrodes atleast in part, and forming a continuous plane between the firstelectrodes, wherein a pixel has at least one of the first electrode andthe second electrode.
 2. The liquid crystal display of claim 1, whereinthe second electrode of a pixel is connected to adjacent pixels.
 3. Theliquid crystal display of claim 2, wherein both the first electrodes andthe second electrode comprise transparent conductive material.
 4. Theliquid crystal display of claim 1, wherein either of the firstelectrodes and the second electrode comprise transparent conductivematerial.
 5. The liquid crystal display of claim 1, further comprising athird electrode formed on the second substrate.
 6. The liquid crystaldisplay of claim 5, wherein the third electrode has an opening.
 7. Aliquid crystal display, comprising: first and second substrates oppositeeach other; a liquid crystal layer inserted between the first and thesecond substrates; and first and second electrodes which are formed onthe first substrate and electrically insulated from each other, whereina rearrangement region, where molecules of the liquid crystal layer arere-arranged by an electric field generated when voltages are applied tothe first and the second electrodes, is formed at least in part on thefirst or the second electrode, and a portion of the rearrangement regionformed on the first or the second electrode serves as a part of adisplay region.
 8. The liquid crystal display of claim 7, wherein themolecules in the rearrangement region have a twist angle and a tiltangle.
 9. The liquid crystal display of claim 7, wherein the firstelectrode overlaps the second electrode at least in part.
 10. The liquidcrystal display of claim 7, wherein the electric field has paraboliclines of force located between the first electrode and the secondelectrode, and the electric field on the first electrode or the secondelectrode has vertical and horizontal components.
 11. The liquid crystaldisplay of claim 7, wherein width of the first electrode is equal to orlarger than width of the second electrode, and the rearrangement regionon the first electrode serves a part of the display region.
 12. Theliquid crystal display of claim 11, wherein the first electrode istransparent.
 13. The liquid crystal display of claim 12, furthercomprising first and second polarizing plates attached respectively toouter surfaces of the first substrate and the second substrate, andwherein light passing through one of the first and the second polarizingplates, passes through the display region and reaches the other of thefirst and the second polarizing plates.
 14. The liquid crystal displayof claim 7, wherein the liquid crystal layer has either positive ornegative dielectric anisotropy.
 15. The liquid crystal display of claim14, wherein long axes of liquid crystal molecules in the liquid crystallayer are either perpendicular or parallel to the first and the secondsubstrates when no voltage is applied to the first and the secondelectrodes.
 16. An liquid crystal display, comprising: first and secondsubstrates facing each other; a liquid crystal layer between the firstand the second substrates, a plurality of scanning signal lines and datalines on the first substrate, the scanning signal lines and the datalines being electrically insulated from and intersecting each other; aplurality of thin film transistors on the first substrate, each thinfilm transistor having a gate electrode connected to the scanning signalline, a source electrode connected to the data line, and a drainelectrode; a plurality of pixel electrodes which are formed on the firstsubstrate and connected to the drain electrodes of the thin filmtransistor; and a plurality of common electrodes which are formed on thefirst substrate and electrically insulated from the pixel electrodes,wherein the thin film transistor switches image signal from the dataline responsive to scanning signal from the scanning signal line totransmit the image signal to the pixel electrode, and wherein arearrangement region, where molecules of the liquid crystal layer arere-arranged by an electric field generated when voltages are applied tothe common and the pixel electrodes, is formed at least in part on thecommon or the pixel electrode, and a portion of the rearrangement regionformed on the common or the pixel electrode serves as a part of adisplay region.
 17. The liquid crystal display of claim 16, wherein thepixel electrodes overlap the common electrode in part to form a storagecapacitor.
 18. The liquid crystal display of claim 16, furthercomprising an insulating layer between the pixel electrodes and thecommon electrodes.
 19. The liquid crystal display of claim 18, whereinthe pixel electrodes are located under the insulating layer, and thecommon electrodes are located on the insulating layer.
 20. The liquidcrystal display of claim 18, wherein the pixel electrodes are located onthe insulating layer, and the common electrodes are located under theinsulating layer.
 21. The liquid crystal display of claim 20, furthercomprising a main connection connecting the common electrodes.
 22. Theliquid crystal display of claim 21, further comprising a redundantconnection formed on the main connection.
 23. The liquid crystal displayof claim 21, further comprising a redundant connection formed under themain connection.
 24. The liquid crystal display of claim 21, wherein themain connection is located on the common electrodes.
 25. The liquidcrystal display of claim 16, further comprising a light blocking filmcovering a region between the data line and the common electrodes andthe pixel electrodes adjacent to the data line.
 26. The liquid crystaldisplay of claim 16, wherein the pixel electrodes and the commonelectrodes are located in the same plane.
 27. The liquid crystal displayof claim 16, further comprising a plurality of color filters on thesecond substrate and a black matrix which is formed on or under thecolor filters and has a plurality of openings exposing the colorfilters, and wherein area of the openings varies depending on colors ofcorresponding color filters.
 28. The liquid crystal display of claim 27,wherein each color filter has one of red, green and blue colors, and thearea of the openings exposing the color filters having blue color islarger than the area of the openings exposing the color filters havingred and blue colors.